1. Field of the Invention
The present invention relates to an electromagnetic switch and is more particularly concerned with an electromagnetic switch which is particularly suited for use in a coaxial type starter for starting the engine of a vehicle.
2. Discussion of Background
A coaxial type starter for starting an engine has been constructed as disclosed in Japanese Unexamined Utility Model Publication No. 105461/1988. The structure of the electromagnetic switch in such conventional coaxial type starter will be explained with reference to FIGS. 6 and 7.
The coaxial type starter includes a d.c. motor 1 having an output rotary shaft 2, and an electromagnetic switch 3. The electromagnetic switch 3 can be arranged at the rear end of the d.c. motor 1 to slide the output rotary shaft 2, and to supply power from a battery to the d.c. motor 1 when the key switch (not shown) of the vehicle is closed. The electromagnetic switch 3 is mainly constituted by a casing 4, a forward and a backward core 5a and 5b forming a magnetic path together with the casing 4, a plastic bobbin 6 supported by the cores, an exciting coil 7 wound on the bobbin 6, and a plastic cylindrical plunger 8 slidably arranged in the inner passage of the bobbin 6.
The cylindrical plunger 8 has its inner side integrally provided with an inner plate 8a. The inner plate 8a has its central portion connected to one end of a plunger rod 9. The plunger rod 9 has its other end inserted from the rear end of the d.c. motor 1 into a hollow armature rotary shaft of the d.c. motor 1. The plunger rod 9 works to transmit the shifting force of the plunger 8 to the output rotary shaft 2 through a spring 10 which is arranged in the bore of the output rotary shaft 2. The plunger rod 9 has a sleeve 11 mounted thereon at the side where the plunger rod 9 is connected to the inner plate 8a of the plunger 8. On the sleeve 11, a movable contact 13 is slidably carried through an insulating member 12.
In such electromagnetic switch 3, the connecting terminal portion (switch terminal) of the exciting coil 7 to the key switch in general has such structure that a rear bracket 14 of the starter is provided with a cutout at the side facing the electromagnetic switch to position at the front side, i.e., the d.c. motor side of the forward core 5a a terminal molded member 16 prepared by molding a terminal plate 15 as shown in FIG. 7. The terminal molded member 16 is fitted into the cutout, the inner end of the terminal plate 15 is connected to one of the opposite leads of the exciting coil 7 led out forwardly through e.g. an opening formed in the forward core 5a, and the outer end 15a of the terminal plate 15 is connected to leads from the key switch.
The conventional switch terminal structure as stated earlier has a problem wherein the entire axial length of the electromagnetic switch is great because the terminal molded member 16 is arranged closer to the d.c. motor 1 than the forward core 5a in terms of space.